1990 V4 runs on two cylinders at low RPMs

[goodmariner85]

The kits were 28 dollars on amazon. Supposedly Johnson Evinrude, and that's what was written on the bags. And maybe BRP. Unfortunately, I tossed the bags. The old floats had the OMC M molded in. The new floats just have a number molded in. I did keep both old floats and gaskets and one pin and seat.

I tried removing the float, inserting the pin and dripping carb cleaner in the seat. I did not see any leak back into the input port. Not a very precise test though. Lifting the pin a bit does let it leak through.

Regarding warping, that's a good point. I just now put them on a flat granite surface and applied moderate pressure on two screw holes. The biggest gap I found with a feeler gauge was 0.019 inch on one and 0.020 inch on the other. That's with no gasket. I have a lower-range torque wrench that I have not used yet. I'll have to find a phillips attachment.

 

[tphoyt]

It’s a pretty common problem on those plastic bowels. Replacing them with the updated aluminum bowels would be the way go.

 

[goodmariner85]

From the little bit of searching around on line, it looks like it's fairly common.

 

[goodmariner85]

If I could get the boat running and the bowls were just dripping some, I'd be a lot happier. For five or ten minutes, then I'd curse at the bowls and replace them.

 

[goodmariner85]

I used blue loctite and tightened them till snug and then a bit more. (Next time I'll count fractions of a turn). I thought it should be sealed pretty well. Hooked them up the fuel manifold and an assistant worked the primer bulb. There was a lot of leaking at the gaskets. I alternated tightening a bit and working the bulb. Looks like all the leaking stopped except for a hint of something at one gasket that didn't even form a drop. I might just call it good. I don't know if I tightened the screws a "normal" amount, or if the covers are warped but you can still tighten enough to get a bit more life out of them. I'll check gaskets again tomorrow when there is more light.

Nothing came out of the vent or jets in the carbs so maybe the floats and needle valves are working. (Or maybe me moving the unsecured carbs around knocked the floats free! I'll find out soon enough.)

 

[ct1762@gmail.com]

I used blue loctite and tightened them till snug and then a bit more. (Next time I'll count fractions of a turn). I thought it should be sealed pretty well. Hooked them up the fuel manifold and an assistant worked the primer bulb. There was a lot of leaking at the gaskets. I alternated tightening a bit and working the bulb. Looks like all the leaking stopped except for a hint of something at one gasket that didn't even form a drop. I might just call it good. I don't know if I tightened the screws a "normal" amount, or if the covers are warped but you can still tighten enough to get a bit more life out of them. I'll check gaskets again tomorrow when there is more light.

Nothing came out of the vent or jets in the carbs so maybe the floats and needle valves are working. (Or maybe me moving the unsecured carbs around knocked the floats free! I'll find out soon enough.)

you really should get the little aluminum factory float gauge tool. makes it alot easier. I ALWAYS blow into the fuel inlet with a rubber hose with the carb both inverted and right side up to make sure its sealing and flowing. drop doesnt matter as long as its opening the needle. height when inverted in the real important part. I also have a couple aluminum brand new float bowls in stock.

 

[goodmariner85]

I wasn't able to find anyone selling the float gauge tool online. I wondered why the drop matters, just to keep the float from striking the cover? Even if I get the motor running, I imagine that it won't be optimum if the float level (not drop) is a little off.

 

[ct1762@gmail.com]

I wasn't able to find anyone selling the float gauge tool online. I wondered why the drop matters, just to keep the float from striking the cover? Even if I get the motor running, I imagine that it won't be optimum if the float level (not drop) is a little off.

people will argue, but so what if the float touches the bottom? makes no difference. if it did, alot more motors would have issues. i do see # 324891 is out of stock everywhere. I wonder how hard it would be to make one out of hard plastic? probably not very!

 

[goodmariner85]

> I ALWAYS blow into the fuel inlet with a rubber hose with the carb both inverted and right side up

I'll try to remember this. I really want to find ways to test everything without reinstalling the carbs.

I saw a post on some forum a few days ago of measurements taken from the float level tool so you can make your own. But I don't think I have the right tools to make one.

 

[goodmariner85]

Put the rebuilt carbs on the fuel manifold today in the light. Gaskets leaked still. Tightened screws till fuel stopped running out around the gasket to the outside of the carb. Then, working the primer bulb, the lower carb flooded again. Pump slowly, fuel runs out the brass tubes. Pump a little harder or faster and it comes out the brass tubes and the vent hole as well.

Everything looked great before I replaced the kit parts. And the kit parts look just like the old ones. The only thing that doesn't look good is the warped float chamber. Of course I can't see that the gasket seals on the *inside* are good. If the seal on the inside where the fuel inlet passage mates to the carb body is not good, fuel can run past it and fill the float chamber no matter if the needle valve is closed.

I put the float chamber on a granite counter top and pressed lightly at the screw holes. Under the fuel inlet fitting, the gap was 20 mil.
I taped 600 grit sandpaper to a granite counter. Sanded using a circular motion and checked until the biggest gap measured about 1 or 1 1/2 mil.

Cleaned the dust out and checked jets again. Put it back together and tried to blow into the inlet fitting. In upright as installed position, air gets through. Inverted, no air gets through. I forgot to test by blowing before I started sanding.

The other carb may be ok, but marginal at best, so I will sand it too. If this works I may be able to put off new bowls for a while. I already had to invest in tools and parts this summer for the boat.

Thanks for all the advice. If this works, @racerone put me on the right track.

 

[goodmariner85]

Update: I sanded the mating surface on both of the plastic float chambers. Reinstalled carbs. Now primer bulb goes firm when pumping. No visible signs of leaking fuel.

Started motor. It was idling much higher than it did before the problem. So I turned the idle adjustment stop screw out all the way, so it's not hitting the stop with the fast idle lever all the way down. I thought it maybe still idled a bit too high. My tachometers are broken again; been working on that. But when idling on the water in forward gear, it seems to idle more slowly and smoothly than it has since I got the boat (and work on the broken engine constantly) in June. I mean, in the past, if I tried to idle that slow, the motor would have died.

Ran at WOT for about 1 minute, then there was sudden loss of power and the engine began to run rather rough at about half the max rpms (again, no tach) still at WOT. So I backed the throttle off, still rough and got to my destination in about 1 or 2 minutes. A few hours later took about a five minute trip home on the boat. It ran rough still with any throttle. So I idled all the way, and it sounded fine.

I'll take the engine cover off tomorrow and look for the new problem. I did not yet zip tie the hoses at the manifold. But, I doubt that's causing this problem.

I did find a 1/16 inch fuel hose that was torn off the nipple on the block. Either right above the lower carb or the upper, I don't recall. There was about 1/2 inch long length of the 1/16 inch hose from the nipple to a tee. The port side branch of the tee ran back toward the cylinders but I didn't trace it all the way. That line is pulled pretty tight.

I pulled the broken stub off of the nipple and pushed the remaining hose onto it. But it's jagged, and too short. So I need to replace it. I may have already popped off.

I've been trying to find out about the system that these hoses and tee are part of. I have the OMC manual. But, I haven't been able to find anything there yet. In an exploded parts diagram there is something similar that is part of the "drain system". I also read about fuel recirculation systems and oil recirculation systems. Crankcase lubrication, etc. Also various valves called "check valves", but depending on the diagram, these look completely different and are in different places.

I already did replace the broken 1/8 inch hose that goes on the fitting on the bottom of the air silencer. I've heard this referred to as a fuel return hose, and also a drain hose, and also just air silencer hose.

 

[jimmbo]

Redo the Compression, Spark across a 7/16" Gap, Tests. While the plugs are out, look for any Bridging of the gap, and any Aluminium specks on them

 

[jimmbo]

Those small Hoses that attach to Fittings on the Block are likely part of the Oil Recirculation System, Some of Fittings are Check Valves

Any hose coming off the Air Silencer would be a Drain, for any fuel that spills out of the Carbs, when the engine is tilted up.

Also see if all the carbs are getting Fuel, and that the Main Jet on each of them is Clear. A plugged Jet, will result in the Cylinder it feeds, being starved of Oil.

 

[goodmariner85]

The sudden loss of power yesterday happened when the link between the carbs jumped out of the upper retainer clip. Retainer seems worn. I've been trying different configurations of zip ties to hold it in (I'll order another clip) The boat ran really well for several minutes at high speeds and idle speed.

Then it began to run very poorly. I checked plugs (they're all light brown with no apparent damage or buildup) and was about to check compression when I noticed fuel was leaking. It was the top carb flooding and leaking. I removed the top carb. It failed the inverted blowing test that it had passed before installing it. I tightened the screws holding the plastic chamber to the carb. Did the blow test again. Seemed good. Installed the carb. Checked with primer bulb. Saw no leaks or flooding at the carbs. It's not easy to get the bulb firm because there is an intermittent air leak at the fittings on tank, and an intermittent fuel leak somewhere near the bulb.

Every time I fix one of these problems the low speed performance changes a lot. Yesterday it idled great. But after reinstalling the carbs for the last time, I noticed the carbs were not opening from the fully closed position at the same time. I played with the plates a little to try to improve it.

Most recently it runs a bit rough and shaky at lower throttle settings. Idle is kind of erratic, not terrible, but not predictable and smooth. It seems to run well near and at WOT. In fact max speed today was 23 mph. The previous max speed when it was running ok a few weeks ago was 21 mph.

I worked on it for about 7 hours day. Most of yesterday too. Next time, some things to do are recheck spark and compression, do at least the first parts of the link and sync: Throttle Valve Synchronization and Cam Follower Pickup.

Also, I have been horsing the throttle and shift cables around repeatedly. They may need some kind of adjustment. I haven't really tried that yet.

 

[goodmariner85]

The bottom carb is a little wet around the gasket, upper carb dry. I don't see any fuel leaking enough to make a drop or run anywhere. I still don't trust that the seal is good everywhere it should be. At some point I'll get new metal float chambers.

I did the throttle valve synch and adjust cam follower pickup. Then I could idle in forward gear at 630 rpm (I dried out my spark plug tach), and 650 is recommended. And got 4300 rpm at WOT, which is as much as I ever got. Sounded and felt pretty smooth over the whole range. I never got it to idle at 650 before without dying so something is working better. It ran well only after warming up. It popped and surged and died suddenly for a while before getting there. I'll have to diagnose that soon. Maybe vacuum leak, or...

Next time I started it, it started hard, died and then wouldn't start. I played around with the toothed wheel at the retainer for the throttle cable and turned in the idle screw a bit. It's kind of ok now.

But I think getting the throttle working well from the remote control all the way to the cam roller is another another issue. The main problem here was a flooded carburetor. I'll call it temporarily solved with a rebuild kit and sanding the warped bowl.

 

[goodmariner85]

A final note: I adjusted both the toothed wheel where the throttle cable is anchored to the motor and the idle stop screw. I started the motor several times over a few days. It starts and idles well indefinitely at low rpm. Seems fairly smooth at all speeds.

 

[ct1762@gmail.com]

A final note: I adjusted both the toothed wheel where the throttle cable is anchored to the motor and the idle stop screw. I started the motor several times over a few days. It starts and idles well indefinitely at low rpm. Seems fairly smooth at all speeds.

if you have ANY sort of air leak it WILL starve the motor of fuel! my suggestion is to get a brand new hose and bulb at this point and stick it deeply in a can of premix and run the motor at full throttle with an assistant. that motor should NOT be idling with the idle stop screw not touching the spark advance lever! if it does, there is air being introduced into the fuel, or leaking from either the upper and or lower crank seals, the block halves, or the intake. it sounds most likely (i forgot if this is a 60 degree motor or an old crossflow) that its either leaking from the spaghetti seals in the intake, or if its a crossflow getting air into the fuel.

 

[racerone]

A 1990 model can only be a crossflow.

 

[ct1762@gmail.com]

A 1990 model can only be a crossflow.

yes. didnt pay attention to year

 

[brodmann]

I bought carb kits from Amazon a few weeks ago and had the exact same problem. Once I took them off and took the bowls off and compared the new parts with the ones I took off, I noticed that the needles were almost 1/8' shorter than the stock ones that I took out.
You can test the needle/seat by using a piece of fuel line connected to the fuel inlet on the carburetor. With the bowls blow into the hose and see if you hear air flowing. Then turn the carb upside down and the air flow should be shut off. Pretty easy test.